1) Field on the Invention
The present invention relates to a polycarbonate resin with a remarkably reduced oblique incidence birefringence, excellent moldability, excellent transcription and good transparency and an optical article used the same. The polycarbonate resin is applicable to uses of general molding of various materials such as medical instrument parts, food vessels, drinking bottles, photoreceptors for electro-photography, toner transfer belts, binders for dye and pigment, gas permeation membranes, toys, materials for window and building, safeguarding materials, OA apparatuses and portable telephones and boxes, and particularly, suitable to the production of optical articles such as optical discs including compact disc, laser disc, optical card, MO disc, digital versatile disc and near field recording optical disc, optical lenses including pick-up lens, spectacle lens and camera lens, optical films and optical sheets including cover layer for near field recording medium and optical filter, optical information transmission media including optical fiber and optical waveguide and photoconductive boards.
2) Prior Art
Recently, a bisphenol A type polycarbonate resin has been widely used as optical materials such as optical disc materials by utilizing its transparency, heat resistance, hydrolysis resistance and dimension stability. However, use of a polycarbonate resin as optical materials caused some problems. Among performances as optical materials, birefringence to change properties of incidence light caused the most important problem.
In order to reduce birefringence, various polycarbonate resin materials have been developed (Japanese Patent Kokai (Laid Open) Nos. 60-215020 and 62-181115). However, also in these developments, reduction of birefringence was not sufficient. Further, recently, reduction of oblique incidence birefringence whose improvement is difficult by controlling molding conditions has been required.
On the other hand, optical disc materials containing polyorganosiloxane have been developed (Japanese Patent Kokai (Laid Open) No. 3-106931). However, in these materials, when the polyorganosiloxane content is increased, transparency to be required for an optical disc could not be maintained, Thus, satisfactory reduction of birefringence could not be attained because the polyorganosiloxane content could not be increased.
Further, in the blend of some resins different in refractive index from each other, white turbidity occurred since it was difficult to disperse uniformly them, so that there occurred problems that use of replaced article in production of other sorts was limited and recycling was difficult.
An object of the present invention is to provide a polycarbonate resin with a remarkably reduced oblique incidence birefringence, excellent moldability, excellent transcription and good transparency and an optical article used the same.
As a result of extensive studies to solve above-mentioned prior art problems, the inventors have found that a copolymerization resin derived from specific three kinds of bisphenols and a mixture of said copolymerization resin and conventional bisphenol A type polycarbonate resin can be used as high quality optical materials with a remarkably reduced oblique incidence birefringence, excellent moldability, excellent transcription and good transparency, and accomplished the present invention.
That is, the present invention provides a polycarbonate resin obtained by reaction of a compound represented by the following general formula (A), a compound represented by the following general formula (B), a compound represented by the following general formula (C) and a carbonic acid ester-forming compound, wherein an amount of a compound represented by the general formula (A) is 30 to 80% by weight to total amount of a compound represented by the general formula (A) and a compound represented by the general formula (B) and a compound represented by the general formula (C) is 1 to 80% by weight to total amount of a compound represented by the general formula (A), a compound represented by the general formula (B) and a compound represented by the general formula (C) and an intrinsic viscosity of said polycarbonate resin is 0.2 to 1.0 dl/g; 
wherein R1, R2, R3 and R4 are, each independently, hydrogen, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an aralkyl group having 7 to 17 carbon atoms and when said group has carbon atom, said group can have an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms as a substituent(s); 
wherein R5, R6, R7 and R8 are, each independently, hydrogen, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an aralkyl group having 7 to 17 carbon atoms and when said group has carbon atom, said group can have an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms as a substituent(s); R9, R10, R11 and R12 are, each independently, hydrogen, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an aralkyl group having 7 to 17 carbon atoms and when said group has carbon atom, said group can have an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms as a substituent(s); R13 is an aliphatic group having 1 to 6 carbon atoms or absent; X is xe2x80x94SiO(R14)(R15)xe2x80x94, xe2x80x94SiO(R16)(R17)xe2x80x94, a homopolymer of xe2x80x94SiO(R14)(R15)xe2x80x94 or xe2x80x94SiO(R16)(R17)xe2x80x94 having an average polymerization degree of more than 0 and 200 or below or a random copolymer of xe2x80x94SiO(R14)(R15)xe2x80x94 and xe2x80x94SiO(R16)(R17)xe2x80x94 having an average polymerization degree of more than 0 and 200 or below; R14, R15, R16 and R17 are, each independently, hydrogen, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an aralkyl group having 7 to 17 carbon atoms and when said group has carbon atom, said group can have an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms as a substituent(s); 
wherein R18 and R19 are, each independently, hydrogen, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an aralkyl group having 7 to 17 carbon atoms and when said group has carbon atom, said group can have an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms as a substituent(s);
Y is; 
wherein R20 and R21 are, each independently, hydrogen, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms, or an aliphatic ring or a heterocycle in combination of R20 and R21 and when said group has carbon atom, said group can have an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atoms as a substituent(s) and a is an integer of 0 to 20.
The invention will be described in detail below.
Examples of the carbonic acid ester-forming compound include phosgene and bisaryl carbonates such as diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-tolyl carbonate, di-p-chlorophenyl carbonate and dinaphthyl carbonate and a combination of two species of the compounds thereof or above.
The polycarbonate resin of the present invention can be produced by reaction of the compound represented by above-mentioned general formula (A) (hereinafter, xe2x80x9ccompound of formula (A)xe2x80x9d), the compound represented by above-mentioned general formula (B) (hereinafter, xe2x80x9ccompound of formula (B)xe2x80x9d), the compound represented by above-mentioned general formula (C) (hereinafter, xe2x80x9ccompound of formula (C)) and a carbonic acid ester-forming compound. Known processes for producing a polycarbonate resin to be derived from bisphenol A, e.g., a process comprising a direct reaction between bisphenols and phosgene (phosgene process) or a process comprising transesterification between bisphenol and a bisaryl carbonate (transesterification process) can be applied.
Among the phosgene process and the transesterification process, it is preferable to apply the phosgene process, considering reactivity between the compound of formula (A) and the compound of formula (B).
In the phosgene process, the reaction of the compound of formula (A), the compound of formula (B), the compound of formula (C) and phosgene is performed usually in the presence of an acid bonding agent and a solvent.
Examples of the acid bonding agent include pyridine and alkali metal hydroxides including sodium hydroxide and potassium hydroxide.
Examples of the solvent include methylene chloride, chloroform, chlorobenzene and xylene.
Further, in order to promote polycondensation, a catalyst including tertiary amines such as triethylamine is added. In order to adjust polymerization degree, monofunctional compounds including phenol, p-t-butyl phenol and p-cumyl phenol alkyl-substituted phenols, hydroxy benzoic acid alkyls, and alkyl oxy phenols are added as molecular weight modifier.
If necessary, a small amount of antioxidants including sodium sulfite and hydrosulfite and a small amount of branching agents including phloroglucine, isatin bisphenol, 1,1,1-tris(4-hydroxyphenyl) ethane and xcex1,xcex1xe2x80x2,xcex1xe2x80x3-tris(4-hydroxyphenyl)-1,3,5-triisopropyl benzene may be added.
The reaction temperature is usually in the range of 0 to 150xc2x0 C. and preferably in the range of 5 to 40xc2x0 C. The reaction time is usually 0.5 minutes to 10 hours and preferably 1 minute to 2 hours, depending on the reaction temperature. It is preferable to maintain pH of the reaction system to 10 or above during the reaction.
In the transesterification process, a mixture of the compound of formula (A), the compound of formula (B), the compound of formula (C) and bisaryl carbonate is reacted under a reduced pressure at a high temperature. In this reaction, a monofunctional compound(s) including p-t-butyl phenol, p-cumyl phenol alkyl-substituted phenols, hydroxy benzoic acid alkyls and alkyl oxy phenols may be added as molecular weight modifier.
The reaction is performed usually at a temperature of 150 to 350xc2x0 C. and preferably 200 to 300xc2x0 C. Phenols by-produced by transesterification and derived from bisaryl carbonate are distilled off preferably under a final reduced pressure degree of 1 mmHg or below outside the reaction system. The reaction time is usually about 1 to 10 hours, depending on the reaction temperature or the reduced pressure degree. It is preferable to perform the reaction under the atmosphere of an inert gas such as nitrogen, argon, etc. If necessary, an antioxidant(s) and a branching agent(s) may be added.
Examples of the compound of formula (A) include 9,9-bis(4-hydroxy-2-methylphenyl) fluorene, 9,9-bis(4-hydroxy-3-methylphenyl) fluorene, 9,9-bis(4-hydroxyphenyl) fluorene, 3,6-dimethyl-9,9-bis(4-hydroxyphenyl) fluorene, 9,9-bis(3-methoxy-4-hydroxyphenyl) fluorene, 9,9-bis(3-ethoxy-4-hydroxyphenyl) fluorene, 9,9-bis(3-ethyl-4-hydroxyphenyl) fluorene, 4,5-dimethyl-9,9-bis(4-hydroxyphenyl) fluorene, 9,9-bis(3-phenyl-4-hydroxyphenyl) fluorene, 3,6-dimethyl-9,9-bis(3-methyl-4-hydroxyphenyl) fluorene and 3,6-diphenyl-9,9-bis(4-hydroxyphenyl)fluorene. Among them, 9,9-bis(4-hydroxyphenyl) fluorene, 9,9-bis(4-hydroxy-3-methylphenyl) fluorene and 9,9-bis(4-hydroxy-2-methylphenyl) fluorene are preferable. A combination of two species of the compounds thereof or above may be used.
Examples of the compound of the formula (B) include the compounds represented by the below structural formulas and a combination of two species of the compounds thereof or above. 
It is preferable that X contains 1 to 100 dimethylsiloxanes or 1 to 100 diphenylsiloxanes and is a random copolymer thereof. Among them, particularly, xcex1,xcfx89-bis[3-(o-hydroxyphenyl) propyl] polydimethyldiphenyl random copolymer siloxane and xcex1,xcfx89-bis[3-(o-hydroxyphenyl) propyl] polydimethylsiloxane are preferable.
Examples of the compound of formula (C) include 4,4xe2x80x2-biphenyl diol, bis(4-hydroxyphenyl) methane, bis(4-hydroxyphenyl) ether, bis(4-hydroxyphenyl) sulfone, bis(4-hydroxy-3-methylphenyl) sulfone, bis(4-hydroxyphenyl) sulfoxide, bis(4-hydroxyphenyl) sulfide, bis(4-hydroxyphenyl) ketone, 1,1-bis(4-hydroxyphenyl) ethane, 2,2-bis(4-hydroxyphenyl) propane (bisphenol A;BPA), 2,2-bis(4-hydroxyphenyl) butane, 1,1-bis(4-hydroxyphenyl) cyclohexane (bisphenol Z;BPZ), 2,2-bis(4-hydroxy-3-methylphenyl) propane (dimethyl bisphenol A), 2,2-bis(4-hydroxy-3,5-dimethylphenyl) propane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane(bisphenol AP;BPAP), bis(4-hydroxyphenyl) diphenylmethane, 2,2-bis(4-hydroxy-3-allylphenyl) propane and 3,3,5-trimethyl-1,1-bis(4-hydroxyphenyl) cyclohexane. A combination of two species of above-mentioned compounds or above may be used. Among them, particullarly, 2,2-bis(4-hydroxyphenyl) propane is preferable.
When the phosgene process is applied to the present invention, it is possible to inject phosgene in the presence of a tetraammonium salt in order to perform efficiently the reaction. Examples of tetraammonium salt include tetramethylammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, tetraethylammonium bromide and tetra-n-butylammonium iodide, among which trimethylbenzylammonium chloride and triethylbenzylammonium chloride are preferable. It is preferable that the amount of tetraammonium salt is usually 0.0005 to 5 mol % to total amount of bisphenols to be used.
Further, when a molecular weight modifier is used in the present invention, monohydric phenol is preferable. Examples of the molecular weight modifier include phenol, alkyl-substituted phenols including butyl phenol, octyl phenol, nonyl phenol, decanyl phenol, tetradecanyl phenol, heptadecanyl phenol and octadecanyl phenol; alkyl hydroxy benzoates including butyl hydroxy benzoate, octyl hydroxy benzoate, nonyl hydroxy benzoate, decanyl hydroxy benzoate and heptadecanyl hydroxy benzoate; alkyl oxy phenols including butoxy phenol, octyl oxy phenol, nonyl oxy phenol, decanyl oxy phenol, tetradecanyl oxy phenol, heptadecanyl oxy phenol and octadecanyl oxy phenol. The amount of the molecular weight modifier is 0.1 to 50 mol % and preferably 0.5 to 10 mol % to total amount of bisphenols.
The polycarbonate resin thus synthesized can be molded by known molding methods including extrusion molding, injection molding, blow molding, compression molding and wet molding. It is preferable that the intrinsic viscosity [xcex7] of the polycarbonate resin is in the range of 0.2 to 1.0 dl/g since it is desirable that it can be readily extrusion-molded or injection-molded as an optical material to mold an optical article. Particularly, when a high cycle molding is required, it is preferable that it is in the range of 0.2 to 0.6 dl/g.
It is preferable that the amount of the compound of formula (A) is 30 to 80% by weight to total amount of the compound of formula (A) and the compound of formula (B), considering curvature, strength and low birefringence of the mold article. When the amount of the compound of formula (A) is below 30% by weight, curvature of the disc molded article becomes large, whereas above 80% by weight strength is decreased and crack occurs during disc molding.
It is preferable that the amount of the compound of formula (C) is 1 to 80% by weight to total mount of the compound of formula (A), the compound of formula (B) and the compound of formula (C), considering a resin replacement in a molder, transparency and low birefringence of the molded article. When the amount of the compound of formula (C) is below 1% by weight, remarkable white turbidity occurs in a blend with a conventional bisphenol A type polycarbonate. Consequently, in case of production apparatus of other sorts to use the material in a molder in which a conventional bisphenol A type polycarbonate is usually used, necessity to disjoint and wash the apparatus occurs, so that operation efficiency of the apparatus is lowered and a return after cleaning of the apparatus is delayed. Furthermore, there are defects that it substantially becomes impossible to mix a conventional bisphenol A polycarbonate in order to reduce a production cost and a replaced article at the time of exchange to other sort becomes opaque, so that recycling use is limited. When the amount of formula (C) is above 80% by weight, the value of birefringence becomes insufficient.
When the polycarbonate resin of the present invention is extrusion molded or injection molded, too large or too small flowability causes problems in molding. It is preferable that the polycarbonate resin of the present invention for extrusion molding has the range of flow rate 1xc3x9710xe2x88x922 to 15xc3x9710xe2x88x922 cc/sec measured with a flow tester (nozzle diameter 1 mm, length 10 mm) at 280xc2x0 C. under 160 kgf/cm2. When the flow rate is outside the range of 1xc3x9710xe2x88x922 to 15xc3x9710xe2x88x922 cc/sec, a dimension precision of the molded article is deteriorated. Further, it is preferable that the polycarbonate resin of the present invention for injection molding has the range of flow rate 3xc3x9710xe2x88x922 to 90xc3x9710xe2x88x922 cc/sec measured by above-mentioned measuring flow tester and conditions. When the flow rate is below 3xc3x9710xe2x88x922 cc/sec, flowability is deteriorated, so that failure filling into a mold and a flow mark sometimes occur. When the flow rate is above 90xc3x9710xe2x88x922 cc/sec, failure releasing from a mold and curvature readily occur.
It is preferable that the molding temperature in extrusion molding and injection molding of the polycarbonate resin is, respectively, 230 to 320xc2x0 C. and 240 to 380xc2x0 C.
It is preferable that the polycarboante resin is highly purified in the same manner as in conventional polycarbonate for optical disc. In detail, it is purified so as to satisfy as much as possible criterions including dusts of diameter 50 xcexcm or above: substantially undetected, dusts of diameter 0.5 to 50 xcexcm: 3xc3x97104 or below, inorganic and organic residual chloride: 2 ppm or below, residual alkali metal: 2 ppm or below, residual hydroxyl group: 200 ppm or below, residual nitrogen content: 5 ppm or below and residual monomer: 20 ppm or below. Post treatments such as extraction for removal of low molecular weight substances and removal of a solvent are sometimes performed.
Regarding the compound of formula (A), the compound of formula (B), the compound of formula (C) and a carbonic ester-forming compound as raw materials, it is preferable to use materials reduced impurities and isomers as much as possible.
In the polycarbonate resin of the present invention, in order to ensure stability and mold releasing be required during extrusion molding or injection molding, if necessary, antioxidants such as hindered phenols and phosphites; lubricants and mold releasing agents including silicons, fatty acid esters, fatty acids, fatty acid glycerides and natural fats and oils including bees wax; light stabilizers such as benzotriazoles, benzophenones, dibenzoyl methane and salicylates and antistatic agents such as polyalkylene glycols and fatty acid glycerides may be used together with the polycarbonate resin.
Further, in order to reduce cost and recycle, a mixture of the polycarbonate resin with an ordinary polycarbonate resin(s) other than the polycarbonate resin may optionally be used within the range not to impair performances. Although the range not to impair performances is different depending on purposes to be used, in addition to above-mentioned properties as a molding material, it is preferable to satisfy at least one and preferably at least two conditions of a 30 degree oblique incidence light birefringence of below 110 nm, a photoelastic sensitivity of below 70xc3x9710xe2x88x9222 m2/N and total light transmissivity of 80% or above of a molded article of thickness 3 mm.
The present invention will be described in more below, referring to Examples, which are not intended to limit the scope of the present invention.
Each properties were measured according to the following methods.
Birefringence
The measurement was performed for an injection molded optical disc substrate of a polycarbonate resin sample with auto-Ellipsometer, manufactured by k.k., Mizojiri Kogaku Kogyo, in Japan by a light of 30 degree oblique incidence angle and wave length 632.8 nm.
Photoelastic Sensitivity
A cast film of thickness 50 xcexcm was prepared from a polycarbonate resin powder sample. The measurement was performed for the cast film with auto-Elliposometer, manufactured by k.k., Mizojiri Kogaku Kogyo, in Japan under a load of 300 to 1100 g in a wave length of 632.8 nm.
Transcription
The measurement was performed for an injection molded optical disc substrate of a polycarbonate resin sample with an atomic force microscope NV2100, manufactured by Olympus Co.
Intrinsic Viscosity [xcex7]
Intrinsic viscosity [xcex7] [dl/g] was measured for a polycarbonate resin solution of 0.5 g/dl concentration in methylene chloride solvent at Huggins""s constant of 0.45 at a temperature of 20xc2x0 C.
Total Light Transmissivity and Haze
Total light transmissivity (%) and haze (%) were measured for an injection molded board article of a polycarbonate resin sample with HM-100, manufactured by Murakami Color Technology Research Laboratory in Japan by a transmission light of 1.9 mmxcfx86.
Haze(H) is calculated as follows:
Tp=Ttxe2x88x92Td 
H=(Td/Tt)xc3x97100 
Tt: total light transmissivity
Tp: parallel light transmissivity
Td: diffusion light transmissivity